Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$66.40	7.650%	$71.4796	$71.48	$71.50	$71.50
Purchase #2	$159.37	8.857%	$173.4854	$173.49	$173.50	$173.50
Purchase #3	$164.27	13.613%	$186.6321	$186.63	$186.65	$186.60
Purchase #4	$233.84	10.705%	$258.8726	$258.87	$258.85	$258.90
Purchase #5	$158.81	4.752%	$166.3567	$166.36	$166.35	$166.40
Purchase #6	$234.27	8.796%	$254.8764	$254.88	$254.90	$254.90
Purchase #7	$72.71	10.256%	$80.1671	$80.17	$80.15	$80.20
7 purchase totals =	$1,089.67		$1,191.8699	$1,191.88	$1,191.90	$1,192.00